I thought I would post this solution here because I have been frustrated (and fuming) for months since I lost MIDI contact with my Korg Triton Taktile 49. I normally use Logic 10.4 but recently loaded the free trial of 10.5. This worked fine with the Korg - midi and DAW controls all behaving. When the trial finished and I reverted to my previous version of Logic my Korg lost Midi contact with Logic. No sound, nothing. After hours of installing and uninstalling drivers from Korg my only solution was to start Logic - reset all midi drivers - quit and restart Logic again and then it would work but without keyboard DAW controls. I recently solved this when I discovered that the Apple MIDI driver was the one to use! I uninstalled the KORG driver using the uninstaller provided by Korg, restarted the Mac with Korg USB unplugged then plugged it in and started Logic and now all is back to normal. Sorry if this is obvious but I had three calls to MAC geniuses during this problem and at no time did anyone offer this as a solution.